Changes of the serum antibiotic levels during open heart surgery (ceftazidim, ciprofloxacin, clindamycin)

BACKGROUND

Wound, mediastinal and intracardiac infections are still very serious complications of open-heart surgery. The incidence of it is still in the range of 0.4%-5%. The aims of our study were to assess the adequacy of regimen using ceftazidim (CTZ), ciprofloxacin (CPF) and clindamycin (CLIN) as prophylactic antibiotics and to verify whether cardiopulmonary bypass (CPB) can modify the time of antibiotic serum concentrations. That is why the serum levels of them were measured during open heart procedures.

METHODS

The prospective study comprised 75 consequent coronary patients randomized in to three groups receiving 1 g of CTZ or 400 mg of CPF or 900 mg of CLIN i.v. with anesthesia induction. Routine coronary surgery with left internal mammary artery harvesting, moderate body hypothermic (30 degrees C) CPB with crystaloid cardioplegia was performed. Serum antibiotic levels were determined before application, with skin incision, prior CPB induction, after cardioplegia infusion, every 20 minutes of CPB, prior end of CPB, in time of chest closure. Conventional cylinder-plate microbiological assay was used for antibiotic level measurement.

RESULTS

All serum antibiotic concentrations showed a sharp decrease immediately after starting CPB and lasted until CPB ended. After initiating of CPB after cardioplegia administration serum concentrations of CTZ (105 min after initial dose) decreased by, on average 55%, CPF (97 min) by 42% and CLIN (116 min) by 78%.

CONCLUSION

CPB can modify the time course of antibiotic serum concentrations. The serum levels of CTZ at the end of the longest procedures were found to be below the MICs for some of the suspected pathogens. We recommend to use higher antibiotic doses for prophylaxis and to administer the second dose with protamin sulphate to obtain maximum concentration in newly formed blood clots.

[Kinetics of ceftazidime in prophylactic administration during cardiopulmonary bypass]

Serum ceftazidime levels were followed in 21 patients in which routine coronary bypass surgery with cardiopulmonary bypass was performed. Each patient received one gram of ceftazidime intravenously with anesthesia induction. Antibiotic concentrations were estimated using the microbiologic assay diffusion plate method. The average operation time was 220 +/- 41 minutes (range 130-310). The start of cardiopulmonary bypass was 86 +/- 21 minutes and the full flow time was 104 +/- 21 minutes after starting of ceftazidime application. It can be stated that the decline of ceftazidime serum levels after starting of cardiopulmonary bypass was faster in comparison with standard serum curves of this antibiotic. The concentrations of ceftazidime at the end of some operations were under the supposed minimal inhibitory concentrations for some microorganisms possibly implicated. No infection was recorded.

[Development of resistance and utilization of fluoroquinolones in a university hospital]

The results of a retrospective study in the Faculty Hospital, Hradec Králové (FHHK) show a steep increase in the consumption of fluoroquinolones in the course of six years. Since 1989, when 360 defined daily doses (DDD) were administered, the consumption increased to 2,825 DDDs in 1992 and 52,162 DDDs in 1995. At the same time, resistance to ofloxacine and ciprofloxacine was increased many times in some bacterial species isolated from patients admitted to FHHK. In the strains Pseudomonas aeruginosa, resistance to ofloxacine increased from 3% to 38% in 1995, in Serratia marcescens from 13% in 1992 to 30% in 1995. A marked increase was observed also in Acinetobacter calcoaceticus. In the naturally highly sensitive species E. coli and Klebsiella pneumoniae no increase in resistance has been observed yet, in Enterobacter cloaceae resistance slightly increased (from 0% in 1992 to 7% in 1995). Due to the fact that in FHHK fluoroquinolones take the first place in the consumption of antibiotics at present, an increase in resistance can be expected also in these bacteria in the future. Investigation of changes in resistance due to the consumption of fluoro-quinolones is a suitable model of a pharmacoepidemiological study (DUE-Drug Utilisation Evaluation) as the relationship of the consumption of a drug and its effect can be observed practically since the introduction of fluoroquinolones into the market.